Thanksgiving week is one of the most dangerous times to drive. With millions of Americans hitting the roads to visit friends and family over the holiday, a disproportionately high number of fatal motor vehicle accidents will affect some Californians this week.

A number of different things contribute to the big statistical surge in dangerous car accidents. USA Today reports that the volume of cars on the road is one big cause. Almost 40 million people will travel more than 50 miles for holiday visits and AAA estimates that 90% of these travelers will go by car. With more people driving long distances on the roads, the opportunities for mistakes multiply.

On top of this, many drivers will be rushed to reach their destinations. Some speed-related accidents will also happen while people are hurrying to finish errands to prepare for the holiday. Rushing appears to be particularly bad for the Thanksgiving holiday for some reason – in at least one state, speed contributed to twice as many fatal crashes as other weeks.

Other drivers will be traveling in relatively unfamiliar areas and driving long hours to reach far-away destinations in time. The combination of unfamiliar roads and fatigue-related mistakes can easily cause dangerous crashes.

In 2010, 431 people died in deadly wrecks on Thanksgiving Day. The whole rest of the week saw a spike in highway fatalities as well.

Pay close attention on the roads this week and remember to drive safely.